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This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

A diet high in whey protein outperformed two other isocaloric diets, one of which was high in non-whey protein, for weight reduction, HbA1c improvement, and better peak glucose levels in patients with type 2 diabetes.

Note that a study author cautioned that whey protein is not a meal substitute, explaining that a whey-based milkshake would replace other proteins traditionally consumed during breakfast.

BOSTON -- A diet high in whey protein outperformed two other isocaloric diets, one of which was high in non-whey protein, for weight reduction, HbA1c improvement, and better peak glucose levels in patients with type 2 diabetes, researchers reported here.

After 12 weeks, participants in the whey protein diet group lost an average of -7.6 kg, had HbA1c levels lowered from 7.8 to 6.9, and a peak glucose of 174 mg/dL versus patients in the any protein group (-6.1 kg, HbA1c of 7.1, and peak glucose 206 mg/dL), reported Daniela Jakubowicz, MD, of Tel Aviv University, and colleagues.

"Recent reports have shown that whey protein has a greater lowering effect on postprandial hyperglycemia (PPHG) than any other source of protein like soy, tuna, or eggs," Jakubowicz explained.

"High-energy protein breakfast (tuna, egg, soy), medium lunch, and small dinner is a successful method for weight loss for decreasing HbA1c, and for decreasing over the day PPGH," she told MedPage Today. "Now we're showing that the same diet, but with whey, is more efficient, and has a more powerful effect on reducing PPHG than other proteins."

"In addition, whey increases the glucose uptake in the muscle," Jakubowicz said. "The most important application of this study is that the breakfast has to be big to increase metabolism and decrease the hunger -- not everybody has time to do this, and a lot of diabetics aren't hungry in the morning' some even have nausea."

But Jakubowicz pointed out that making a shake with whey protein powder, which is a byproduct of milk during cheese production, and milk can take mere minutes to prepare and consume; people can then supplement that breakfast with other foods later in the morning.

"You meet all the necessary protein to lose weight without all the preparation," she said.

However, she cautioned that whey protein is not a meal substitute, explaining that a whey-based shake would replace other proteins traditionally consumed during breakfast. "This is important," she said. "It helps people to go through with consumption of big breakfast."

"There are several mechanisms that can explain this effect," she added. "Whey protein may decrease the PPHG. Insulinogenic amino acids rapidly absorbed to the blood that directly stimulates insulin secretion. Whey protein stimulates secretion of incretin GLP-1 that in turn also stimulates insulin secretion. Whey also increases the glucose uptake into the muscle."

The author used an 80% whey protein concentrate for this study. All of the whey protein powders work the same and the competition between brands and isolates has no bearing on performance, Jakubowicz said. "According to what I read in the scientific report, the effect on glucose, satiety, and insulin, there's no difference, plus the 80% [formula] is less expensive."

For the study, 48 participants with an average age of 59 were enrolled. They all had type 2 diabetes and were being treated with diet modification and metformin. They were randomized to one of three isocaloric diets for 12 weeks.

Each of the three diets consisted of three meals per day, with approximately 660 calories for breakfast, 560 calories for lunch, and 280 calories for dinner.

The lunch and dinner contents were identical between the diets. For one diet (WBdiet), 17 participants consumed 42 g of whey-based protein for breakfast. In the second diet (PBdiet), 16 participants consumed 42 g of non-whey protein for breakfast. And in the CBdiet, 15 participants had a diet high in carbohydrates and only 17 g of protein.

After 12 weeks, total weight loss was greatest for those on the WBdiet, at an average of -7.6 kg, compared with -6.1 kg for PBdiet group, and -3.5 kg for the CBdiet group.

HbA1c levels, which were 7.8 at baseline, decreased across all groups, but a larger reduction was found among the WBdiet group at 6.9 compared with 7.1 for the PBdiet group, and 7.4 for CBdiet group (P<0.001).

Peak glucose measures were lowest for members of the WBdiet group (174 mg/dL), followed by participants in PBdiet group (206 mg/dL). Peak glucose was highest for the CBdiet group (251 mg/dL, P<0.0001 for all).

WBdiet participants had superior GLP-1 and satiety after each meal, followed by PBdiet participants, and CBdiet participants (P<0.0001 for all values), and meal challenge response to ghrelin and hunger were most suppressed for WBdiet participants, followed by PBdiet, and CBdiet levels (P<0.0001 for all values).

Jakubowicz and co-authors disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner